In recent years, along with the progress in fine circuit patterns in the process for producing semiconductor integrated circuits, a photoresist material having high resolution and high sensitivity is demanded. As the circuit patterns become fine, a short wavelength of a light source for an exposure apparatus becomes essential. In an application as a base polymer for a resist material to lithography employing an excimer laser of 250 nm or shorter, a polyvinyl phenol type resin, an alicyclic acrylic type resin, a polynorbornene type resin (e.g., description of WO01/63362 or the like), a fluorinated resin (e.g., description of WO00/17712 or the like) or the like has, for example, been proposed, but satisfactory resolution, sensitivity and high dry etching resistance have not been obtained.
It is an object of the present invention to provide a base polymer for a resist material having excellent properties, particularly excellent dry etching resistance.